Abstract
Abstract In the present study the relationships of oxygen consumption to cardiac output, stroke volume, and heart rate were observed in normal subjects and patients with hyperdynamic circulatory states before and after the assumption of the head-up tilt posture. Under a variety of circulatory stresses, including the augmented metabolic demand of exercise and hyperthyroidism, the hemic demand of anemia, and the low peripheral resistance of arteriovenous communication, the assumption of the head-up tilt posture was associated with a diminished cardiac output and stroke volume and a rise in heart rate. These observations indicate the presence of an over-all decrease in the cardiac output response in the upright stance and are consistent with the thesis that the central blood volume performs an important regulatory function in cardiovascular dynamics.
Published Version
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